The present invention relates to a stereoscopic endoscope system and a TV imaging system for an endoscope which are used to observe an object three-dimensionally.
In recent years, endoscopes each having an elongated insertion unit thereof inserted in a body cavity for observation of an organ in the body cavity and making it possible to use if necessary a treatment appliance inserted in a treatment appliance channel to conduct various curative procedures have been adopted widely. Moreover, industrial endoscopes have been widely utilized for observation, inspection, or the like of flaws, corrosion, or the like inside a pipe in a boiler, gas turbine, engine, chemical plant, or the like or inside a body of an automobile engine.
The endoscopes include a flexible endoscope whose insertion unit is flexible and inserted in a curved body cavity through a mouth or the like in order to observe or diagnose a lesion in the body cavity, and a rigid endoscope whose insertion unit is rigid and inserted linearly to an intended region.
In case the flexible endoscope is of an optical type, a flexible image guide fiber is used as an image conveying means. The rigid endoscope has an excellent target-finding ability owing to its rigid insertion unit, wherein a relay optical system is usually used as an image conveying means to produce an optical image.
The endoscopes including the rigid endoscope fall into a type in which an optical image is observed directly by naked eyes and a type in which an optical image picked up by a solid-state imaging device such as a charge-coupled device (CCD) serving as an imaging means is displayed in a monitor screen for observation.
With advancements in surgical procedures, endoscopic surgery, in which a small orifice is created in the abdomen in order to observe the abdominal cavity or conduct an operation thereon using an endoscope, is prevailing as a substitute for conventionally-adopted laparotomy. Almost all the foregoing endoscopes are designed to visualize a body cavity as a planar image that cannot give depth perception.
As far as the known endoscopes for viewing a planar image are concerned, it is hard to observe minute irregularity on the surface of, for example, an inner wall of a body cavity which is a very important diagnostic indication. In an effort to overcome this drawback, a stereoscopic endoscope in which optical systems are arranged in an endoscope, which is designed for producing a planar image for observation, in such a manner that three-dimensional observation is enabled has been proposed.
The optical systems for an endoscope enabling stereoscopy fall into three types described below.
First, a stereoscopic endoscope 10 of, as shown in FIG. 1, a dual-objective dual-relay optical system type has been disclosed in Japanese Patent Laid-Open No. 6-160731. The stereoscopic endoscope 10 is configured by juxtaposing two identical optical systems.
In the stereoscopic endoscope 10, as shown in FIG. 1, images 13a and 13b formed by objective optical systems 12a and 12b incorporated in a scope unit 11 are transmitted by a given distance by conveying optical systems 14a and 14b formed with systems of relay lenses. The images are then recomposed into parallel rays by lenses 15a and 15b and transmitted to a TV camera unit 16.
The images transmitted to the TV camera unit 16 are formed on imaging planes of two imaging devices 18a and 18b by way of image formation lenses 17a and 17b, whereby optical images are produced. Reference numeral d1 denotes a spacing between two optical axes that is comparable to a parallax.
Secondly, as shown in FIG. 2, a stereoscopic endoscope 20 of a single-objective single-relay optical system type is described in Japanese Patent Laid-Open No. 6-167658. In the stereoscopic endoscope 20, a system of relay lenses serving as an objective optical system and conveying optical system is formed with a single optical system that is axially symmetric.
In the stereoscopic endoscope 20, as shown in FIG. 2, a pair of right and left aperture stops 23a and 23b and image formation lenses 24a and 24b are located at a position 22 of image formation at the back end of the system of relay lenses 21 so that the aperture stops will have a spacing corresponding to a parallax d2 between them. An image is therefore spatially split into two portions. Thus, a pair of right and left images having a parallax between them are formed on two imaging devices 25a and 25b, whereby optical images are produced.
Thirdly, the present applicant has disclosed a stereoscopic endoscope 30 of a dual-objective single-relay optical system type as shown in FIG. 3 in Japanese Patent Laid-Open No. 7-261099.
In the stereoscopic endoscope 30, as shown in FIG. 3, a pair of right and left systems of lenses are used as first groups of lenses 32a and 32b of an objective optical system 31 and placed so that aperture stops of the systems will have a spacing d3 between them. A second group 33 of lenses of the objective optical system 31, and systems of relay lenses 34a, 34b, and 34c serving as a conveying optical system are each formed with a single optical system that is axially symmetric. An image passing through entrance pupil formation lenses 35 located at the back end of these systems of relay lenses 34a, 34b, and 34c is spatially split by aperture stops 36a and 36b. Resultant right and left images are formed on two imaging devices 38a and 38b by a pair of right and left image formation lenses 37a and 37b, whereby optical images are produced.
One of the advantages of the stereoscopic endoscope 10 of a dual-objective dual-relay optical system type shown in FIG. 1 is that a three-dimensional image can be produced merely by juxtaposing normal optical systems designed for an endoscope. For optimizing three-dimensionality, the spacing dl between the optical axes of objective optical systems should merely be varied. In this case, the optimization can be achieved irrespective of specifications including an angle of view. The stereoscopic endoscope of this type can be designed more easily than the stereoscopic endoscope 20 of a single-objective single-relay optical system type shown in FIG. 2.
By contrast, one of the drawbacks of the stereoscopic endoscope 10 lies in that since the right and left optical systems are constructed independently, the number of parts is large. Consequently, assembling is complex. Moreover, a difference in magnification between right and left images occurs deriving from an error of each part, and a shift of a focal point are large, and fine adjustment is required for normal stereoscopy.
One of the advantages of the stereoscopic endoscope 20 of a single-objective single-relay optical system type shown in FIG. 2 is that the structures of an objective optical system and system of relay lenses are identical to those of normal optical systems designed for an endoscope. Therefore, while right and left images are sharing the same optical path, a change of an image deriving from errors caused during manufacturing occurs in the right and left images in the same manner. A difference in magnification between the right and left images and a shift of a focal point are therefore small. Moreover, since the number of parts is small, assembling efficiency is good. When as described in Japanese Patent Laid-Open No. 6-59199, a system of relay lenses is integrated into a scope unit and image formation lenses and imaging devices are integrated into a TV camera unit, the orientations of images can be corrected by turning the units relative to each other.
On the other hand, one of the drawbacks of the stereoscopic endoscope 20 is that three-dimensionality cannot be determined irrespective of specifications including an angle of view. The spacing between right and left entrance pupils of aperture stops that determines three-dimensionality is determined by an angle of view of an objective optical system, a numerical aperture of a system of relay lenses, a spacing between the aperture stops, and the like. Normally, the diameter of an aperture stop of an objective optical system is smaller than that of a system of relay lenses. As long as the outer diameter of an insertion unit is identical to that of the stereoscopic endoscope 10 of a dual-objective dual-relay optical system type shown in FIG. 1, three-dimensionality is poorer.
One of the advantages of the stereoscopic endoscope 30 of a dual-objective single-relay optical system type shown in FIG. 3 is that three-dimensionality can be optimized irrespective to specifications including an angle of view by varying the spacing d3 between optical axes of the two first groups of lenses of the objective optical system. Moreover, since right and left images share the same optical path in the range from the second group of lenses of the objective optical system to the entrance pupil formation lenses, a difference in magnification between the right and left images and a shift of a focal point are small. Besides, since the number of parts is small, assembling efficiency is good.
By contrast, a drawback of the stereoscopic endoscope 30 lies in that when lenses ending with the entrance pupil formation lenses are integrated into a scope unit and lenses succeeding the entrance pupil formation lenses are integrated into a TV camera unit, the orientations of images cannot be corrected by turning the units relative to each other. This is because the positions of the right and left aperture stops of the scope unit are fixed by the first group of lenses of the objective optical system. Light beams are therefore obstructed by the turning.
As mentioned above, the three typical types of stereoscopic endoscopes have both advantages and disadvantages. The endoscopes have therefore been used selectively according to the purpose of use.
However, even in case the stereoscopic endoscopes are used selectively according to the purpose of use, the drawbacks below occur.
In the stereoscopic endoscope 20 and stereoscopic endoscope 30, scope units that are mutually different in terms of a diameter of an aperture stop or a spacing between aperture stops; that is, in terms of an outer diameter can be switched and coupled with one TV camera unit.
This is because that the positions of the pair of the right and left aperture stops and the spacing between the optical axes of the image formation lenses in the stereoscopic endoscope 20 shown in FIG. 2 are fixed. Therefore, if a scope unit whose relay optical system has an aperture stop of a small diameter is mounted, light beams are obstructed. On the contrary, if a scope whose relay optical system has an aperture stop of a large diameter is mounted, light rays that cannot be extracted increase in number. This leads to a larger amount of wasted light. When a plurality of scope units having different diameters are prepared and used selectively according to the purpose of use, it becomes necessary to prepare a plurality of TV camera units in line with the scope units. This poses a serious problem costwise.
Moreover, even if any type of TV camera unit is used, it is impossible to replace the corresponding scope unit with any other type of scope unit and couple it with the TV camera unit. Since the TV camera units are mutually incompatible, when a plurality of scope units are prepared to cope with different purposes of use, it is required to prepare a plurality of TV cameras. This poses a problem costwise.
Moreover, whichever type of TV camera unit is used, the TV camera unit is dedicated to a stereoscopic endoscope. The TV camera unit is incompatible with the one for a rigid scope used for normal observation.
In any type of TV camera unit, the TV camera unit has a pair of right and left image formation lenses. This leads to a large number of parts. Moreover, since there is a difference between right and left images, focusing or the like is needed.
A stereoscopic endoscope system in accordance with the first invention comprises: a scope unit including at least one objective optical system located in an elongated insertion unit, and at least one conveying optical system for conveying an object image formed by the objective optical system; and a TV camera unit including one image formation optical system for imaging a light beam emanating from the scope unit, and an imaging device for picking up images passing through the image formation optical system. The stereoscopic endoscope system is characterized in that the scope unit and TV camera unit are detachable from each other, and that an image disuniting member for disuniting a plurality of images is incorporated in the TV camera unit.
According to the first invention, the image disuniting member incorporated in the TV camera unit detachable from the scope unit can disunite a plurality of images.
A TV imaging system for an endoscope in accordance with the second invention comprises a scope unit having an elongated insertion unit that can be inserted in a narrow region and a TV camera unit that can be attached to the scope unit. The TV imaging system is characterized in that the TV camera unit includes a single image formation optical system, a stop splitting member for temporally splitting an aperture stop of the image formation optical system, and an imaging device for photoelectrically transferring images formed by the image formation optical system, and that the member for temporally splitting the aperture stop temporally switches a state, in which one of two areas constituting the aperture stop of the image formation optical system is transparent and the other area is interceptive, and a state in which the one of the two areas is interceptive and the other area is transparent.
According to the second invention, the aperture stop of the image formation optical system can be split temporally by temporally switching the state, in which one of two areas constituting the aperture stop of the image formation optical system is transparent and the other area is interceptive, and the state in which the one of the two areas is interceptive and the other area is transparent.